Magnetically controlled rotating indicator



Dec. 31,1968 J slLVERMAN ET AL 3,419,858

MAGNETICALLY CONTROLLED ROTATING INDICATOR Filed Aug. 14, 1967 INVENTORIS ALVIN J. SILVERMAN ALBERT DIAMOND Maw ATTORNEY United States Patent 3,419,858 MAGNETICALLY CONTROLLED ROTATING INDICATOR Alvin J. Silverrnan, Massapequa, and Albert Diamond,

Plainview, N.Y., assignors to Vernitron Corporation,

Farmingdale, N.Y., a corporation of New York Filed Aug. 14, 1967, Ser. No. 660,399 9 Claims. (Cl. 340-378) ABSTRACT OF THE DISCLOSURE The device of the instant invention includes an annular array of selectively energizable salient poles having a permanent magnet rotor mounted centrally of the poles. An indicia-carrying drum may rotate about the poles with the rotor and carry at least one magnetic formation slightly olfset with respect to the magnetic axis of the rotor.

BACKGROUND OF THE INVENTION In the field of read-out devices of the permanent-magnet motor-type construction, certain problems have persisted. For example, in the use of pulsed power, such indicating devices have heretofore been subject to irritating dither, resulting from slight movement of the indicating member between a home position under power and a slightly offset detent position after power is removed. This offset or slightly out-of-line detent position has heretofore been found essential to avoid a dead-center position and permit ISO-degree rotor rotation.

Another difficulty in prior-art devices was the need for a substantial air gap between rotor and poles, which reduced and limited the possible torque obtainable, both under power and by detent action of a residual field.

SUMMARY Accordingly, it is an important object of the present invention to provide an indicating device of the type described which overcomes the above-mentioned difficulties, wherein a pulsed signal may be employed without appreciable or apparent dither, while being capable of 180- degree rotor rotation upon energization of an opposite pole or upon reversal of polarity, where the system provides for polarity reversal, to minimize the number of coils required per display position.

It is still another object of the present invention to provide an indicator or read-out device of the type described wherein is achieved a substantially increased magnetic torque by reduction of the air gap, for quicker and more positive operation, and reduction in power requirements.

It is still a further object of the present invention to provide an indicating device having the advantageous characteristics mentioned in the preceding paragraphs which is extremely simple in construction, durable and entirely reliable throughout a long useful life, and which can be economically manufactured for sale at a reasonable price.

Other objects of the present invention will become apparent upon reading the following specification and referring to the accompanying drawings, which form a material part of this disclosure.

The invention accordingly consists in the features of construction, combinations of elements, and arrangements of parts, which will be exemplified in the construction hereinafter described and of which the scope will be indicated by the appended claims.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a front elevational view showing an indicating device constructed in accordance with the teachings of the present invention;

FIGURE 2 is a sectional elevational view taken gencrally along the line 7r-2 of FIGURE 1;

FIGURE 3 is a sectional View taken generally along the line 3-3 of FIGURE 2, enlarged for clarity; and

FIGURE 4 is an exploded perspective view of the device of FIGURES 1-3, partly broken away.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularly to the drawing, and specifically to FIGURES 1-3 thereof, an indicating device is there genera-lly designated 10, and includes a generally flat mounting plate 11, which may be of generally rectangular-outline configuration, say having rectangularly arranged thru openings or holes 18, as for mounting fasteners. A journal post or shaft 12 projects centrally from the mounting plate 11, generally normal thereto, and may have its outer portion 13 of reduced diameter, defining an outwardly facing shoulder 14. R0- tatably circumposed about the shaft 12, say about the reduced outer shaft portion 13, is a bearing sleeve 15, which may have its inner end adjacent to a washer 16 circumposed about the shaft portion 13 adjacent to shoulder 14, the outer end of bearing sleeve 15 being retained on shaft 12 by a retainer ring 17, or other suitable retaining means.

Spaced concentrically about the shaft 12, and fixed by any suitable means to the mounting plate 11, is a mounting or spacer ring 20. The ring 20 and plate 11 may be fabricated of non-magnetic material.

A plurality of laminae 21 are arranged in facing engagement with each other, being of annular configuration generally congruent to that of spacer ring 20 and secured thereto to define a magnetic ring 22. The laminations 21 are each further formed with a plurality of radially inward extensions 23, the extensions of each lamination being in respective facing engagement with the extensions of the remaining laminations, and thereby defining radially inwardly extending teeth 24. In the illustrated embodiment, the teeth 24 are equally angularly spaced about the ring 22 and shaft 12, extending radially inwardly from the ring and terminating short of the shaft 12.

circumposed about and carried by each tooth 24 is an electrically conductive coil 25. The coils 25 are thus equal in number to the teeth 24, being shown in the illustrated embodiment as an odd number, namely five. Each coil may be provided with an externally connected conductor, as at 26, the other side of the coils being generally connected to a common connection. As will appear more fully hereinafter, the number of coils 25 and teeth 24 is not critical, and this number may be even or odd. However, an odd number of teeth and coils may provide double the number of indicating positions, to be described below.

Fixedly circumposed about the bearing sleeve 15 is a permanent magnet 30, having a pair of radially oppositely outwardly projecting poles 31 and 32. The permanent magnet 30 may be generally coplanar with the teeth 24 and ring 22, however, such is not necessary to the operation of this invention. The poles 3'1 and 32 of the permanent magnet 30 are advantageously of a cross-sectional configuration substantially similar to that of the teeth 24, for optimum positioning accuracy. Also, it will be apparent from FIGURE 2, that the radial extent of the magnet poles 31 and 32 terminates adjacent to but just short of the radially inwardly extending ends of teeth 24, providing for minimum air gap.

The permanent magnet 30 thus defines a rotor, being rotatable about the axis of shaft 12 on sleeve 15, located centrally within the annular arrangement of teeth 24 and coils 25. In practice, the teeth 24 and coils 25 may be considered as an annular array of salient poles, being selectively activatable by energization of the coils 25, passing current therethrough in a selected direction, as desired.

Externally of the magnetic ring 22, extending circumferentially thereabout and generally concentric therewith, is an indicating drum 35, which may be of non-magnetic material, and provided on its outer periphery with suitable indicia, such as numerical markings shown in FIG- URE 1. The drum 35 may include a disclike end wall 36 extending radially inwardly and terminating in a central sleeve or tube 37 snugly circumposed about or otherwise fixedly secured to the sleeve 15. The tube 37 of drum 35 may have its inner end engaging the hub of rotor 30, and is retained on the sleeve 15 by retaining ring 17. Thus, the drum 35 is rotatable as a unit with the permanent magnet or rotor 30.

Interiorly of the drum 35, say on the inner face of end wall 36, radially outward of the coils 25, there is provided a mounting ring 40 fixedly secured within the drum. A plurality of pins 41 arranged in equally angularly spaced relation about the mounting ring 40 and shaft 12 are carried by the mounting ring, and extend toward but terminate short of the magnetic ring 22. The pins 41 are advantageously fabricated of magnetically soft material. As best seen in FIGURE 2, the pins 41 may be of double the number of poles 24, 25. Further, one diametrically opposed pair of pins 41, the leftmost and rightmost pair as shown in FIGURE 2, are slightly offset from alignment with the poles of permanent magnet or rotor 30. Thus, when the rotor 30 is in substantial alignment with a tooth 24, the alternate pins 41 are each slightly angularly offset from alignment with an adjacent tooth 24. The amount of angular offset is exaggerated in FIGURE 2 for clarity, and specific angular offset may be achieved to meet the design requirements.

In the position of operation shown in FIGURE 2, the leftmost coil 25 has been energized to attract rotor pole 3'1. A magnetic field of relatively great fiux density then passes through the rotor pole 31, leftmost tooth 24, around both the upper and lower branches of magnetic ring 22 and return to the rotor pole 32 through the two rightmost teeth 24. As the flux density is relatively great through this circuit, the leftmost pin 41 which defines a magnetic formation in the circuit is of negligible effect and the rotor pole 31 remains substantially aligned with the adjacent tooth 24. Upon the removal of power from leftmost coil 25, the residual fiux between pole 31 and adjacent tooth 24 is still relatively great, while the effect of magnetic formation or leftmost pin 41 is not appreciable, so that the rotor pole 31 remains aligned with the leftmost tooth 24 and is effectively held or detented in this position without energization or power.

Upon energization of another one of the coils 25 to attract the pole 31, it will be obvious that the rotor 30 will swing into alignment with the energized coil and its associated toooth 24.

It will be appreciated that the pins 41 are in the leakage field thus having no perceptive influence on rotor rotation because of the substantially greater influence of the main field between the permanent magnet rotor 30 and stator tooth 24. However, upon reverse energization of leftmost coil 25, polarity thereof is reversed, thus creating a field opposing the field of the permanent magnet. The net force in the main field between the permanent magnet and stator tooth is thus substantially reduced. Under this condition, the magnetic formation provided by leftmost pin 41, in the position of FIGURE 2, becomes relatively important and effects incipient rotation of rotor 30. More specifically the magnitude of the force of the pin in the leakage field becomes effective and initiates rotor rotation. That is, the pin 41, now under the influence of an effective field, will move to a position in line with the tooth 24 to minimize reluctance thus offsetting the rotor 30 sufficiently to permit its further rotation under the influence of the main field. Movement is completed upon ISO-degree rotation with pole 32 extending leftward in substantial alignment with leftmost tooth 24.

In addition, in the position of FIGURE 2, upon reversed energization of the leftmost coil, the rightmost magnetic formation or pin 41 aids in effecting incipient rotation by its slight angular offset from the axis of permanent magnet poles 31 and 32. Thus, while the device of the present invention, as described hereinbefore, may be operative with a single magnetic formation or pin 41, it is desirable that a pair of diametrically opposed magnetic formations or pins be employed, both for their magnetic action, as well as mechanical balance. Further, in a commercial embodiment, it may be advantageous to provide a plurality of magnetic formations or pins 41, as illustrated.

While the indicating device device 10 may be employed with continuous DC current, an important advantage of the instant invention resides in the elimination of dither or flutter under the use of pulsed current. That is, in the illustrated position of FIGURE 2, as described hereinbefore, the pole 31 remains substantially aligned with the adjacent tooth 24 upon the removal of current from the corresponding coil 25. This occurs because the effect of the leftmost magnetic formation 41 is negligible, as aforesaid. Otherwise stated, the magnetomotive force is stronger in the field between the tooth and the permanent magnet than in the field between the tooth and the magneic formations. Basically there is no apparent difference between power on and detent positions. Hence, pulsed DC current through the leftmost coil 25 serving to attract rotor pole 31 does not cause any visible vibration, flutter or dither of the rotor, or its unitary disc 35. I

Another important advantage is that ISO-degree reversibility is obtained Without the heretofore necessity to enlarge the air gap; thus permitting the smallest possible air gap for maximum torque output and strongest detent force, the latter being an invaluable benefit in resisting the effects of vibration forces.

While an odd number of salient poles 24, 25 has been illustrated and described, it is appreciated that an even number of salient poles may be employed, if desired. However, it is considerable more economical to employ an odd number of poles permitting double the number of positions, rather than an even number of poles permitting only an equal number of positions.

From the foregoing, it is seen that the present invention provides an indicating or read-out device which fully accomplishes its intended objects and is well adapted to meet practical conditions of manufacture, installation, maintenance and use.

Although the present invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is understood that certain changes and modifications may be made within the spirit of the invention and scope of the appended claims.

What is claimed is:

1. An indicating device comprising a fixed annular array of selectively energizable salient poles to form a main field, a permanent-magnet rotor mounted centrally of said poles for rotation to substantial alignment with an energized pole, an indicia-carrying drum mounted for rotation with said rotor, and at least one magnetic formation mounted for rotation with said drum and rotor and slightly offset with respect to the magnetic axis of the latter, said magnetic formation being of small magnetic effect relative to the detenting action of a salient pole with said rotor so as not to appreciably affect rotor alignment with a detenting pole, and the magnetic effect of said formation being relatively enhanced to initiate ISO-degree rotor rotation at least upon reversal of said main field.

2. An indicating device according to claim 1, wherein said salient poles are an odd number equally angularly spaced to provide a number of rotor positions double the number of poles, and said main field being reversed by reversing the polarity of a detenting salient pole.

3. An indicating device according to claim 2, wherein at least a pair of magnetic formations aremounted for rotation with said drum and rotor and slightly offset with respect to the magnetic axis of the latter, whereby a respective one of said magnetic formations will move to a position in line With a corresponding single salient pole tooth upon energization of said salient pole in an opposite direction.

4. An indicating device according to claim 1, said magnetic formation comprising a pin of magnetically soft material carried by said drum and extending toward said array of salient poles.

5. An indicating device according to claim 1, said array of salient poles comprising a magnetic ring, a plurality of angularly spaced teeth extending inwardly from said ring, and a selectively energizable coil circumposed about each of said teeth.

6. An indicating device according to claim 5, said magnetic formation comprising an annulus of non-magnetic material concentric with said rotor, and a pin of magnetic material extending from said annulus toward said magnetic ring.

7. An indicating device according to claim 5, said magnetic formation comprising an annulus of non-magnetic material concentric with said rotor, and a plurality of equally angularly spaced pins of magnetic material extending from said annulus toward said magnetic ring.

8. An indicating device according to calim 1, wherein said salient poles are an even number equally angularly spaced to provide a number of rotor positions equal to the number of poles, and said main field being reversed by energization of a salient pole 180 degrees opposite.

9. An indicating device according to claim 8, wherein at least a pair of magnetic formations are mounted for rotation with said drum and rotor and slightly ofiset with respect to the magnetic axis of the latter, whereby a respecive one of said magnetic formations will move to a position in line with a corresponding single salient pole tooth upon energization of the salient pole 180 degrees opposite.

References Cited UNITED STATES PATENTS 3,109,167 10/1963 MacIntyre et a1. 340-378 JOHN W. CALDWELL, Primary Examiner. HAROLD PITTS, Assistant Examiner.

US. Cl. X.R. 

